1. Field of the Invention
This invention relates generally to semiconductor products manufacturing, and, more particularly, to a method and means for hierarchical organization of run-to-run control parameters.
2. Description of the Related Art
The technology explosion in the manufacturing industry has resulted in many new and innovative manufacturing processes. Todays manufacturing processes, particularly semiconductor manufacturing processes, call for a large number of important steps. These process steps are usually vital, and, therefore, require a number of inputs that are generally fine tuned to maintain proper manufacturing control.
The manufacture of semiconductor devices requires a number of discrete process steps to create a packaged semiconductor device from raw semiconductor material. The various processes, from the initial growth of the semiconductor material, the slicing of the semiconductor crystal into individual wafers, the fabrication stages (etching, doping, ion implanting, or the like), to the packaging and final testing of the completed device, are so different from one another and so specialized that the processes may be performed in different manufacturing locations that contain different control schemes.
One of the most important aspects of semiconductor manufacturing is overlay control. Overlay is one of several important steps in the lithography area of semiconductor manufacturing. Overlay control involves measuring the misalignment between two successive patterned layers on the surface of a semiconductor device. Generally, minimization of misalignment errors is important to ensure that the multiple layers of the semiconductor devices are connected and functional. As technology facilitates smaller critical dimensions for semiconductor devices, the need for the reduction of misalignment errors increases dramatically.
Generally, photolithography engineers currently analyze the overlay errors a few times a month. The results from the analysis of the overlay errors are used to manually make updates to control settings. Some of the problems associated with the current methods include the fact that the control settings such as ASM settings for photolithography processes, are only updated a few times a month. Furthermore, currently, the ASM updates are performed manually.
Generally, a set of processing steps is performed on a lot of wafers on a semiconductor manufacturing tool called a stepper. The stepper communicates with a manufacturing framework or a network of processing modules. The manufacturing framework is connected to an equipment interface. The equipment interface is connected to a machine interface to which the stepper is connected, thereby facilitating communications between the stepper and the manufacturing framework. The machine interface interacts with an automatic process control (APC) system. The APC system initiates a control script, which can be a computer program that automatically retrieves the data needed to execute a manufacturing process. The input parameters that control the manufacturing process are revised periodically in a manual fashion. As the need for higher precision manufacturing processes are required, improved methods are needed to revise input parameters that control manufacturing processes in a more automated and timely manner.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a method is provided for controlling manufacturing processes using a hierarchical system. A first lot of semiconductor devices is processed using a first set of control input parameters. The first set of control input parameters is stored in one of a plurality of hierarchical levels, the first set of control input parameters being available for processing of a second lot of semiconductor devices. Process data is acquired from the processing of the first lot of semiconductor devices. A second set of control input parameters is determined for a subsequent lot of semiconductor devices based upon the acquired process data. The second set of control input parameters is stored in one of a plurality of hierarchical levels, the first and second sets of control input parameters being available for processing of a third lot of semiconductor devices.
In another aspect of the present invention, an apparatus is provided for controlling manufacturing processes using a hierarchical system. The apparatus of the present invention comprises means for processing a first lot of semiconductor devices using a first set of control input parameters, means for storing the first set of control input parameters in one of a plurality of hierarchical levels, the first set of control input parameters being available for processing of a second lot of semiconductor devices, means for acquiring process data from the processing of the first lot of semiconductor devices, means for determining a second set of control input parameters for a subsequent lot of semiconductor devices based upon the acquired process data, and means for storing the second set of control input parameters in one of a plurality of hierarchical levels, the first and second sets of control input parameters being available for processing of a third lot of semiconductor devices.